Cleaning of the surfaces of various types of equipment and structures is often desirable. Numerous processes and cleaning agents are known in the art. The choice of process and agent depends to a great extent on the coating to be removed and on the substrate. In addition, the working conditions and the environmental effects of the process and agent used are becoming increasingly important factors when selecting an optimal cleaning technique.
Sand blasting and other abrasive techniques are quite applicable on hard substrates, but require special arrangements to meet the specification related to environment and working conditions.
Less hard and durable substrates like aluminium, wood and composite materials require processes and cleaning agents which do not cause mechanical or chemical damage to the surface of the substrate.
International Patent Application No PCT/NO93/00137 in the name of Norsk Hydro A. S discloses a wet blasting process which employs an aqueous slurry of precipitated, non-soluble, calcium carbonate. The use of such aqueous wet blasting agents has a number of disadvantages. The aqueous blasting slurries have a tendency to freeze when used in countries where severe winters are encountered. Further, the presence of water in blasting slurries can have the effect of contributing to erosion of the surface being cleaned. This problem is particularly acute when the surface being cleaned forms part of a structure or building. Moreover, the use of aqueous blasting slurries to treat surfaces having electrical components can be particularly hazardous and can cause corrosion.
It is an object of the invention to overcome at least some of the above disadvantages.